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Test Catalog

Test ID: GCT    
Galactosemia Reflex, Blood

Secondary ID A test code used for billing and in test definitions created prior to November 2011


NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.


Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis, carrier detection, and determination of genotype of galactose-1-phosphate uridyltransferase deficiency, the most common cause of galactosemia


Differentiating Duarte variant galactosemia from classic galactosemia


Confirming results of newborn screening programs

Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request

Preferred test to evaluate for possible diagnosis of galactosemia, routine carrier screening, and follow-up of abnormal newborn screening results. Comprehensive reflex test begins with quantitative galactose-1-phosphate uridyltransferase (GALT) enzyme analysis (GALT / Galactose-1-Phosphate Uridyltransferase [GALT], Blood). If quantitative GALT enzyme value is consistent with a diagnosis of or carrier status for galactosemia, DNA analysis of the GALT gene (GAL6 / Galactosemia Gene Analysis [6-Mutation Panel]) is performed to detect the 4 most frequently encountered classic galactosemia alleles (Q188R, S135L, K285N, and L195P) in addition to the N314D (Duarte) and L218L (Los Angeles) variants.

Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)

Test IDReporting NameAvailable SeparatelyAlways Performed
GAL6Galactosemia Gene AnalysisYesNo

Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.

Testing begins with galactose-1-phosphate uridyltransferase (GALT) enzyme analysis. If GALT is > or =24.5 nmol/h/mg of hemoglobin, testing is complete. No molecular test will be performed. If GALT is <24.5 nmol/h/mg of hemoglobin, GAL6 / Galactosemia Gene Analysis (6-Mutation Panel) will be performed at an additional charge.


See Galactosemia Testing Algorithm in Special Instructions.

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test

Method Name A short description of the method used to perform the test

Enzyme Reaction Followed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name

Galactosemia Reflex, B

Aliases Lists additional common names for a test, as an aid in searching

Galactosemia Carrier Testing
Galactosemia Confirmation Test
Galactosemia Enzyme (verify which test)
Galactosemia Gene Analysis
Galactose-1-Phosphate Uridyltransferase (GALT)